This disclosure relates to polycarbonate compositions, and in particular to polycarbonate compositions having infrared (IR) absorbance, methods of manufacture, and uses thereof.
Polycarbonates are useful for applications in which good impact strength, low haze, and high transparency are desired. On such application for which polycarbonates are suitable is protective eyewear, including that designed to limit ocular exposure to potentially damaging radiation. Included in this category is protective eyewear for applications such as, for example, welding, foundry work, glassblowing, and other similar types of hot work, wherein a range of moderate to high intensity infrared radiation is present. Standards, such as European Norms EN 166, EN 169, and EN 171, have been developed as guidelines for the performance of materials and articles for eyewear for protection from infrared radiation, which block the transmission of an amount of the radiation. Both EN 169, which describes requirements for filters for welding and related techniques, and EN 171, which describes requirements for personal eye protection using infrared filters, include different scales identified by number, that correspond to requirements for acceptable amounts of transmittable radiation. The requirements are to the amounts of infrared radiation, and visible and/or ultraviolet radiation, that are allowable for transmission through the protective eyewear. Protective eyewear can be designed according to these individual scale requirements to provide the user of the eyewear with an acceptable level of exposure for a specific application.
To prepare protective eyewear protection for use in the infrared region, also referred to as the IR region (780 to 2000 nanometers) and that meet these standards, additives that absorb and/or dissipate infrared radiation can be added to polycarbonates. Organic infrared shielding additives derived from polycyclic aromatic amines and salts, such as N,N,N′,N′-tetrakis-(p-di-n-butylaminophenyl)-p-phenylenediamine and N,N,N′,N′-tetrakis-(p-di-n-butylaminophenyl)-p-benzoquinone-bis-(immonium-hexafluoroantimonate), can provide absorbance in the infrared; however, such compounds generally lack the thermal and oxidative stability needed to withstand extrusion and molding conditions without decomposition.
What is needed therefore, is a polycarbonate composition that meets at least one of the series requirements of one or both of European Norms EN169 and EN171, and is suitable for use in protective eyewear.
A suitable composition desirably is thermally and oxidatively stable, has good impact strength, and suitable level of haze.